Is there a way to remove end of life modems from my account?

I would like old modems removed from my account plus 2 that I no longer have. I had rented an XB6 T gateway and I would like that one removed, as I returned it using the provided UPS label about a year ago. I also had to return a Netgear CM700 and I got a new one in place of that one as an even exchange. The last modem I would like removed is an old Arris SB6121, as I have no intentions on using that modem ever again, since it will not give me my speed that I pay for.

I also have a Netgear CM1000 that I would like to keep on the account  for my back up modem. 

Recently I have also swapped back to my Netgear CM700, and before on the devices tab for my account it said the full name of the modem, now its just abbreviated as NG CM700. Is there a way to change it back to the full name of the modem?

I have also been swapping the modems out trying to see about why I have instances where my streaming of videos from YouTube would lag down to lower video quality when my speed supports it. My signal levels on both devices have been fine and within spec and logs are quiet for a full several days to weeks. If there is any disconnects then I am not online when it happens. I also dont have any other traffic on my network when I watch streaming content at times.

One last thing. Sevral times when I had issues and went tried to go back to another modem. The self activation thing would work or it would never work. Is there something secuity issue wise where as a hold is put on how many devices you can activate within a given window of time?